Protein binding, DFT/TDDFT calculation and catecholase activity of five coordinated distorted square pyramidal/trigonal bipyramidal Cu(II) complexes

Abstract

Two Cu(II) complexes, [Cu(L1)(OCN)(H2O)] (1) and [Cu(L2)]·H2O (2) [HL1, bis(2-pyridyl carbonyl)amine; H2L2, 2{3-[5-(2-hydroxy-3methoxy)-pent-4-enylamino]-propylimino}methyl-6-methoxy phenol], were synthesized and characterized by single crystal X-ray crystallography, thermal analysis, FTIR and mass spectroscopic techniques. Complexes 1 and 2 show a square pyramidal and trigonal bipyramidal Cu(II) coordination sphere, respectively. In the solid state complex 1 forms hydrogen bonded 1D supramolecular structure and complex 2 forms 1D supramolecular structure with CH…π interactions. Results of experimental electronic absorption and FTIR spectral studies have been compared with the calculated results obtained by density functional theory (DFT) and time dependent density functional theory (TD-DFT) using the CAM-B3LYP functional, with LanL2DZ basis set. Catecholase activity of the compounds have been studied using 3,5-di-tert butyl catechol (3,5-DTBC) as model substrate and found that both of these are active for catalyzing oxidation of 3,5-DTBC to 3,5-di-tert butyl benzoquinone (3,5-DTBQ) in presence of molecular oxygen. Calculated values of the turnover numbers (Kcat) are 29.2 ± 3 and 112.14 ± 5 h−1 for 1 and 2, respectively. The interactions of complexes 1 and 2 with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using electronic absorption and fluorescence spectroscopic methods and the results show that both the compounds interact with BSA/HSA with ground state association process.